Diablo Game Questions Random Crashes, NA?

Twice today my game has crashed completely unexpectedly. I'm trying to do the full bounty run thing, but both times I got about halfway through the 4th act and my game would just crash. I'm still working towards my set, so I can't speed it along, I need to play for roughly an hour, and it hasn't been working today. Is anybody else having this problem, or has Blizz already addressed it?